System Design Basics

System design interviews assess your ability to design large-scale systems. Even if you're not interviewing at FAANG companies, these skills are increasingly important.

What Interviewers Look For

• Ability to break down complex problems
• Understanding of trade-offs in design decisions
• Knowledge of scalability patterns
• Communication and collaboration skills

The System Design Framework

1. Clarify Requirements (5 minutes)

• Functional requirements: What should the system do?
• Non-functional requirements: Scale, latency, availability
• Constraints: Budget, timeline, existing systems

2. Estimate Scale (5 minutes)

• Number of users (DAU/MAU)
• Data size and growth rate
• Read/write ratio
• Peak vs. average load

3. High-Level Design (10 minutes)

• Draw main components and data flow
• Identify APIs between components
• Choose database types (SQL vs. NoSQL)
• Consider caching and CDN placement

4. Deep Dive (15 minutes)

• Pick 1-2 components to detail
• Discuss data models and schemas
• Address bottlenecks and solutions
• Consider edge cases and failure scenarios

5. Wrap Up (5 minutes)

• Summarize the design
• Discuss trade-offs you made
• Mention future improvements

Key Concepts to Know

• Load balancing and horizontal scaling
• Database sharding and replication
• Caching strategies (Redis, Memcached)
• Message queues and async processing
• CAP theorem and eventual consistency
• Microservices vs. monolith

Practice Problems

• Design a URL shortener (like bit.ly)
• Design Twitter's news feed
• Design a ride-sharing service (like Uber)
• Design a video streaming platform (like YouTube)
• Design a chat application (like Slack)